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Liquid tutorial 5.1


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Liquid tutorial 5.1

  1. 1. LIQUID
  2. 2. Properties of Liquid Volume & shape • Has a definite volume but not a definite shape( a liquid retains its volume but not its shape) • A liquid flows to fit the shape of its container. Compressibility • Particles are packed closely have very little empty space between molecules,thus difficult to compress. • Will resist applied external force
  3. 3. Diffusion • The diffusion rate of a liquid is much slower than gas but faster than solids due to: -molecules are closely packed & lower kinetic energy because stronger intermolecular attractive forces between the molecules compared to gases Liquid movement
  4. 4. Viscosity • Viscosity is resistance of liquid to flow. • Viscosity depends on: -stronger intermolecular attractive forces,the more viscous. -the higher the temperature, the lower the viscosity. •The greater a liquid’s viscosity, the more slowly it flows.
  5. 5. Surface tension • The amount of energy required to stretch the surface of a liquid by a unit area. • Molecules on surface are pulled downward & sideways from the neighbouring molecules but not upward away from the surface. • The stronger the intermolecular attractive forces, the higher the surface tension.
  6. 6. Condensation • The process in which a gas transformed into a liquid • According to the kinetic molecular theory: -when the temperature is lower, the kinetic energy of the molecular decreases. -make them get closer, so cannot overcome the intermolecular forces. -more vapour molecules may strike the surface of the liquid to be captured there. -therefore, the gas will condense into the liquid.
  7. 7. Example of condensation
  8. 8. Vaporisation • The process in which liquid is transformed into gas through a surface. • According to the kinetic molecular theory: -liquid molecules gain energy and move quite freely because some molecules have relatively high kinetic energies. -when the kinetic energy is sufficient enough to overcome the attractive forces that bind them, the molecules will loosen themselves and be evaporated off into gas.
  9. 9. Factors of vaporisation process Surface area • The larger the surface area, the higher the chances molecules to escape from the surface. Temperature • When temperature increased, number of molecules that have kinetic energy is increased & escape to form gas. Intermolecular forces. • The weaker the intermolecular forces between molecules.
  10. 10. Vapour pressure • The vapour pressure of a liquid is the pressure exerted by vapour in equilibrium with its liquid in a closed container. • There are two main factors that affect the vapour pressure of a pure liquid: -intermolecular forces in the liquid -temperature
  11. 11. How vapour pressure is exerted??! • Vapour molecules in a closed system • These vapour molecules are in constant random motion continually strike:- -the walls of the container -other vapour molecules -the surface of the liquid molecules • Everytime the vapour molecules hit the wall of the container, pressure is exerted.
  12. 12. Boiling point • The temperature at which the vapour pressure is equal to the external atmospheric pressure. • Occur at the surface and inner part of the liquid • Temperature remains constant during the boiling process even heat is supplied.
  13. 13. Normal boiling point • Occurs when the vapour pressure of the liquid equals to atmospheric pressure at 1 atm. • At the temperature, the vapour pressure of the liquid become sufficient to overcome atmospheric pressure and lift the liquid to form bubbles inside the liquid. • Also known as atmospheric boiling point.
  14. 14. Boiling: A liquid boils at a temp. when the vapor pressure P1 becomes equal to the external pressure P2 above the liquid
  15. 15. Evaporation Vaporization-the process by which a liquid or solid changes to gas. Evaporation- is the process where particles escape from the surface of a non boiling liquid and enters the gas state. ~Evaporation takes place because the particles of liquids have different kinetic energies, therefore some of the particles with higher kinetic energy overcome the intermolecular forces and evaporate to go in the gas phase.
  16. 16. In daily life • Condensation is the change of the physical state of matter from gas phase into liquid phase, and is the reverse of vaporization.[1] It can also be defined as the change in the state of water vapor to water/any liquid when in contact with any surface. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition.
  17. 17. 1. The boiling point of several liquid is given as below : arrange these liquid in order of decreasing vapour pressure.explain your answer : Liquids Boiling points methanol 65 ethanol 78 propanol 97 butanol 117 Boyle’s Law Question1:
  18. 18. 1. Determine whether propanol,CH3CH2CH2OH or prapanal,CH3CH2CH0 has a higher vapour pressure at room temperature. Explain your answers. Boyle’s Law Question2: